Because the adverse reactions associated with treatment of onchocerciasis, loiasis, and lymphatic filariasis can be severe, systemic, and debilitating the mediators of this posttreatment reaction have been identified and quantified. Usually mediated, in part, by the eoinophil, the chemokines associated with eosinophil trafficking in these have been identified using immunocytochemical analysis.The clinical and immunological differences between patients who maintain (for three years) clearance of microfilaremia and those who fail to do so following definitive treatment has been assessed. The data suggest that both immunologically and clinically there are no obvious differences (save for the presence of microfilaremia) between those who remain microfilaria- free and those who are microfilaremic long term after therapy. Diagnostic Studies - PCR-based diagnostic strategies have been developed for Loa loa and Strongyloides stercoralis using recently identified repeated sequences. More importantly, a rapid format card test (based on immunochromatography) has been developed and tested; it shows sensitivities and specificities above 90 percent.